The bottom line is this: if either the origination or termination of a call happens on a device substantially different from a normal PSTN line at the customer premises (for example, an ATA-like device from Vonage and the like) the call basically falls under the realm of an “information service” as far as the laws are concerned and are thus subject to much less regulation than a “telecom service,” which is what calls over the standard PSTN are treated as (e.g. a call between my Qwest lines).

If the VoIP happens “inside the network” somewhere as opposed to at the customer permises, then it’s treated as telecom. If the VoIP is “transparent,” then it’s not really VoIP as far as the US regulators are concerned.